Terminal effectiveness is a primary criterion for projectiles. Depending on the function of the projectile, the impact velocity at the target primarily generally determines the terminal effectiveness of the projectiles, such as fin stabilized, sub-caliber armor piercing projectiles. The aerodynamic drag and related velocity decay during flight affect the impact velocity. In a conventional fin stabilized projectile, a shortening is made of the length of the acceleration transfer interface between sub-caliber projectile and discarding sabot. In this particular disclosure, the sabot is provided with multiple annular or helical grooves that match those on the sub-caliber projectile. Typically, the multiple annular rings or helical grooves occupy a substantial portion on the length of the projectile.
The reduction in length of the acceleration transmitting interface permits its location to a position aft of the point of boundary layer transition from laminar to turbulent flow, leading to low frictional coefficient of the laminar boundary layer over a large portion of the sub-caliber projectile. The resulting reduction in aerodynamic drag is particularly effective for mid caliber projectiles that improve impact velocity. Reference is made, for example, to U.S. Pat. No. 5,413,049.
Generally, conventional projectiles that are provided with sabots, create high velocity fragments after launch as the sabots shatter into pieces and the projectile transitions from aft incident to front incident air stream at high velocity. The shattered pieces from the sabot correspond to the original pieces that made up the sabot assembly. In the specific case of a multi-piece finned projectile that is fired from a 40 mm De-Armer rifle, the sabot assembly has 9 pieces. The sabot shatters apart after muzzle launch into 9 or more pieces at high velocity, posing a hazard to personnel close to the weapon and potentially increasing collateral damage. The shattering of the sabot after launch also creates an airflow disturbance that degrades the aiming accuracy of the projectile and degrades the muzzle velocity and ultimately the impact velocity.
Moreover, the complex assembly of a projectile with a sabot is relatively more costly to fabricate and manufacture. Each component needs to be precisely made since it needs to be assembled with numerous other components, in order to minimize asymmetry and distortion, for achieve structural integrity.
Thus, it is apparent that there exists a need for an improved projectile that presents greater safety than conventional projectiles, and that does not cause fragments to be dispersed at high velocity, during launch from a weapon. The projectile design should maximize impact velocity, terminal effectiveness, and range and aiming accuracy, and it should further be amenable to low cost mass production. The need for such a projectile has heretofore remained unsatisfied.